Felis ISSN 2398-2950

FeLV test

Synonym(s): Feline leukemia virus

Contributor(s): David Godfrey, Kim Willoughby

Overview

  • Presence of certain antigens or virus in blood indicates viremia (circulating feline leukemia virus (FeLV Feline leukemia virus)).
  • Presence of antigen or virus in other body tissues - bone marrow or spleen may be used sometimes to confirm latent infection.
  • Testing is critical to diagnosis and control of FeLV disease Feline leukemia virus disease.

Sampling

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Tests

Methodologies

  • Types of tests available:
    • In-house/screening tests.
      • ELISA tests Enzyme linked immunosorbent assay (ELISA) (commercially available kits) for use in practice laboratories: sample is applied to assay device, solutions are added and after a specified time, a color change matching positive control indicates presence of p27 antigen.
      • 'In practice' immunochromotography (detect monoclonal p27).
      • Rapid immunomigratory (RIM) test for use in practice laboratories.
    • Specialist laboratory tests.
      • IFA (immunofluorescent antibody Indirect immunofluorescence).
      • Virus isolation sensitive and specific but slow.
      • PCR for FeLV proviral DNA is sensitive and specific.
      • PCR for FeLV viral RNA not commercially available as yet.

Availability

  • Widely available.

Validity

Sensitivity

  • Sensitivity is a measure of the proportion of infected cats, as determined by the 'gold standard test' (Virus Isolation, Provirus DNA PCR or IFA) which are detected by the test examined.
  • Most in-house tests have a sensitivity of >85%.
    False negative ELISA and RIM tests can occur. This may be about 10% when they are compared to the Provirus DNA PCR.The sensitivity of viral culture and Proviral DNA PCR are very high.
    The sensitivity of IFA is lower, ie some false negative results are seen in IFA compared to culture and PCR, especially if the leucocyte count is low.

Specificity

  • Specificity is a measure of the proportion of uninfected cats, as determined by the 'gold standard test' (Virus Isolation, Provirus DNA PCR or IFA) which are detected by the test examined.
  • Most in-house tests are very specific (98%). However, when testing a population of cats with a low prevalence of FeLV these false positive results are very important and lead to a signicantly reduced positive predictive value.
    False positive tests occur. There should be a high suspicion of a false positive when testing a healthy cat.
  • IFA, Provirus DNA PCR and virus isolation are very specific.

Predictive value

  • Positive predicative value of screening tests is only around 60%.
  • Negative predicative value of screening tests around 99%.
  • Good if combined with level of suspicion based on clinical evidence, ie high level of suspicion and a positive ELISA, believe result; if high level of suspicion and negative ELISA do Provirus DNA PCR or virus isolation.
  • If possibility of false positive (ie routine screen of healthy cat), do IFA, Provirus DNA PCR or virus isolation.

Result Data

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Further Reading

Publications

Refereed papers

  • Recent references from VetMed Resource and PubMed.
  • Lutz H, Addie D, Belak S et al(2009) Feline leukaemia ABCD guidelines on prevention and management. J Feline Med Surg 11, 565-574 PubMed.
  • Hartmann K, Griessmayr P, Schulz B et al(2007) Quality of different in-clinic test systems for feline immunodeficiency virus and feline leukaemia virus infection. J Feline Med Surg 9, 439-445 PubMed.
  • Hartmann K, Werner R M, Egberink H & Jarrett O (2001) Comparison of 6 in-house tests for the rapid diagnosis of feline immunodeficiency and feline leukaemia virus infections. Vet Rec 149, 317-320.
  • Robinson A et al(1998) Comparison of a rapid immunomigration test and ELISA for FIV antibody and FeLV antigen testing in cats. Vet Rec 142(18), 491-492.
  • Babyak S D et al(1996) Evaluation of a saliva test kit for feline leukaemia virus antigen. JAAHA 32(5), 397-400.
  • Barr M C (1996) FIV, FeLV and FIPV: interpretation and misinterpretation of serological test results. Semin Vet Med Surg (Small Anim) 11(3), 144-153.
  • Jackson M L et al(1996) Feline leukaemia virus detection by ELISA and PCR in peripheral blood from 68 cats with high, moderate, or low suspicion of having FeLV-related disease. J Vet Diagn Invest 8(1), 25-30.


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